The nuns are all from Nigeria, and reside at the convent. Police say 55-year-old Sister Obiama was there alone when the attack happened.
Goodness said the man punched and kicked her. She was taken to a local hospital.
A church sexton said the man had come to the church earlier in the day asking for money and was turned away.
Newark police fanned out across the area bringing back, a one point, a possible suspect in a gray sedan for one of the nuns to try to identify, but police later said no one had been arrested.
Sister Obiama is expected to be released from the hospital later Thursday with some bruises.
(The Associated Press contributed to this report)